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Outline 6

Comparative Physiology- Renner Lecture 6

The nervous system provides means of ________ ___________ between an ______ and the _______ and _______ environment rapid communication, organism, external, internal
what are the three components of the nervous system ? receptors, neurons, effectors
what are receptors? give an example sense organs- ex: rods in retina are specialized photoreceptors, only light/dark vision.
what are neurons? modified epithelial cells that integrate information and are specialized to conduct impulse through specialized excitable membrane to an effector aka motor neuron.
what are effectors? give some examples effect or act on the stimulus in the form of an action. an example is a muscle or an endocrine gland.
single celled organisms (amoeba) and simple multicellular organisms (Phylum Porifera) can respond to stimuli but are not considered nerve cells, why? Because reception of a stimuli, conduction, and effector, are all in one unit. Cell to cell transmission is slow in sponges, and they contain no neurons.
the first evidence of the receptor/conduction function from the effector appears in the _____________________ Phylum Coelenterata
Phylum Coelenterata have specialized cells of ________ origin arranged in a ________________ ectodermal, nerve net
what two major advances that improve the efficiency of the nervous system in higher organisms? 1. cephalization/concentration of sensory organs, receptors in the head region; presence of ganglia (aggregates of neurons) help actively process info. 2. separation of nerve functions into sensory and motor components; result in reflex arc.
Explain what a reflex arc is and why it is useful Sensory neurons that receive input from a receptor, transfer that input to a motor neuron which then activates an effector. It does not include in the brain.
what is the advantage of the addition of interneurons in vertebrates and higher invertebrates to the reflex arc ? it allows the stimulus to be passed on to to multiple effectors
the nervous system of vertebrates contains two classes of neurons what are they? Neurons and neuroglia
if depolarization reaches ___________ it will trigger a/an_________________ threshold, action potential
axon hillock is a region of ____________ integration
The axon is the ___________ portion of the neuron, while dendrites are ______________ units transmitting, receiving
axons generally terminate as a branched structure; branches known as ____________ also emerge from the axon collaterals
What are the general types of neurons? Unipolar, Pseudounipolar, Bipolar, Multipolar
Describe a unipolar neuron, where are they found? It has one process that gives rise to branches. Commonly found in invertebrates, they are present in vertebrates during embryological development. Found in ganglia of adult mammals' autonomic system.
Describe a pseudounipolar neuron, where are they found? initially develop as bipolar but the dendrites and axon fuse during development to form a single process coming out of the soma. Function as sensory neurons in spinal ganglia. Not present in invertebrates since they do not have a spinal cord.
Describe a bipolar neuron, where are they found? It has a single axon and a single dendrite emerging from the soma. Found in retina, and olfactory epithelium.
Describe a multipolar neuron, where are they found? It has a single axon and multiple dendrites. It is the most common type found in vertebrate nervous system. Ex: Purkinjee cell- 150,000 dendritic branches
What are the 5 types of neuroglia? 1. oligodendrocytes 2. schwann cells 3. astrocytes 4. microglia 5. ependymal cells
These neuroglia cells form myelin sheath on axons in the CNS Oligodendrocytes
These neuroglia cells form myelin sheath in the PNS Schwann cells
These neuroglia cells maintain ion balance, degrade neurotransmitters, synthesize neurotransmitters. Astrocytes
This type of neuroglia cells are associated with white matter axon tracks Fibrous astrocytes
These neuroglia cells are phagocytic, they are derived from microphages. Microglia
These neuroglia cells line ventricles of brain, choroid plexus, and secrete CSF Ependymal cells
in which membrane is membrane potential altered and for what purpose? in excitable membranes, it is to allow signal transmission
the action potential is a _________ event membrane
what is meant by depolarization? how does that affect AP? it means that the inside of the cell becomes less negative. When threshold is reached, an AP will be initiated.
Define threshold critical level of depolarization, makes polarity of membrane positive. When reached the AP will occur.
TRUE OR FALSE: The change in membrane potential during AP is long lasting FALSE. It is short lasting
An AP is initiated in an _____________ fashion all or none
TRUE OR FALSE: The amplitude of an AP can be increased by increasing the duration or intensity of the stimulus FALSE. it cannot be increased like that
what is a refractory period? period where a second stimulus will not initiate an action potential
What event drives the membrane potential closer to threshold? The opening of VgNa+ channel that open as a result of depolarization due to stimulus
What value is the membrane potential driven to at the start of an AP? The membrane potential is driven towards the equilibrium potential of Na+ which is +55mV
VgK+ channels in the membrane also open after a ____________ period lag
what two events lead to increased efflux of K+ compared to K+ influx? The opening of VgK+ channels and the inactivation of VgNa+ channels after a brief period of time
what potential is the membrane driven back to? It is driven back to -80mV, the equilibrium potential of K+
What event contributes to the hyperpolarization of the membrane? VgK+ channels staying open for a brief period of time
how are the chemical gradients across the membrane restored? Via Na+/K+ pump
Created by: rusulali97



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